Would an unlocked iPhone change your buying habits?

Apple may be on the verge of offering a factory-unlocked iPhone 4 for sale in the U.S., according to a new report Sunday (via Electronista). Apple already offers the iPhone 4 for sale unlocked in some other countries, so it should be easy for the company to do, but will it affect your buying decision?

Assuming Apple does what it has done in other countries where the iPhone 4 is unlocked to work with any carrier, unlocked versions will likely be sold exclusively through Apple itself, and will come with a fairly steep price tag, since it won’t come with any carrier subsidy. Without a contract, the iPhone 4 starts at $599 for the 16 GB version, and $699 for the 32 GB model. But, of course, you aren’t tied to any service commitment, and you’ll avoid the dreaded early termination fee, which can be as much as $325 for AT&T customers.

But there is a substantial catch. Unlike in other countries, an unlocked GSM iPhone in the U.S. doesn’t present many alternatives for those looking to play outside AT&T’s sandbox. You can’t use the device with Sprint’s network, or Verizon’s, since both are based on CDMA technology, and Apple isn’t planning on offering an unlocked CDMA device for sale in the U.S., according to the report. You can use it with T-Mobile, but you’ll be sacrificing 3G speeds for data traffic, and will instead have to settle on EDGE. Canadians have three choices of major carriers when it comes to 3G GSM service, and as do U.K. smartphone users, by comparison.

But carrier choice isn’t the only reason to opt for an unlocked iPhone. Having a factory-unlocked device makes the process of using it in international destinations easier by far (since you don’t have to resort to potentially risky and unsupported aftermarket unlock procedures), so frequent travellers will appreciate the convenience.

And even if you aren’t a globe-trotter, there are still big advantages to getting your phone factory unlocked, with resale value being possibly the biggest. The market for second-hand iOS devices is always hot, and you should be able to get a higher asking price by selling internationally to markets where the iPhone 4 might not be available, or might be available but prohibitively expensive, so long as you have a factory-unlocked version that buyers can easily use with their local provider.

According to Electronista, AT&T may be encouraging Apple to offer an unlocked version of the iPhone 4 as a way of countering Sprint’s objection to the proposed AT&T / T-Mobile merger. Sprint thinks the deal will give AT&T more control over exclusives with hardware providers, and an unlocked iPhone would make that seem like less of an issue without doing too much to hurt AT&T’s business. But whatever the reason, having an unlocked version available definitely isn’t a bad thing for shoppers.

Would you buy an unlocked version over a carrier-subsidized locked one?